1. Field of the Invention
This invention relates to a concrete paving machine, more particularly a machine for levelling concrete, of the type whereby poured concrete is spread over a pre-determined width and this concrete is equalled at a well-defined thickness.
2. Description of the Related Art
As known, such concrete paving machines are applied for spreading and equalling of concrete, with the intention of forming a floor, plate, road or similar, whereby either or not simultaneously certain profilings can be provided in the formed road, such as a drain, an upstanding edge, a concrete crash barrier, or similar.
It is known that such concrete paving machines generally are composed of a movable frame under which a number of tools is fixed, the aim of which is to distribute the concrete poured in front of the machine, more or less equalling it, vibrating and finally drawing it equal, such that after passing of the concrete paving machine, a completely finished road is created, whereby hereafter one only has to wait for the hardening of the concrete, and eventually provided extension joints will have to be filled.
It is known to equip such concrete paving machines also with a dowel apparatus for providing dowels in the concrete, mostly at the height of the extension joints. Such dowels are reinforcing bars, mostly with a length of approximately 0.5 meters, which are provided in the concrete in the longitudinal direction of the road. Mostly, a whole series of such dowels is provided next to each other, at mutual distances of 20 to 30 cm.
The dowel apparatuses applied hereby are apparatuses which allow to position such series of dowels above the concrete next to each other and to vibrate these dowels subsequently into the concrete. Hereby, the dowel apparatuses are suspended at the concrete paving machine in such a manner that they can remain stationary for a certain period of time in order to vibrate the dowels into the concrete, during which the actual concrete paving machine slowly moves further.
Known embodiments of concrete paving machines with dowel apparatuses are described in EP 0.051.885, EP 0.196.698, and DE 3.811.186.
The invention has a concrete paving machine as its object which is improved in respect to the known embodiments.
To this aim, the invention aims at a concrete paving machine of the above-mentioned type, with as a characteristic that the concrete paving machine is provided with at least one dowel apparatus, whereby this dowel apparatus is movable according to the working width.
As the dowel apparatus is movable, the advantage is created that the dowel apparatus must not necessarily extend over the entire maximum working width of the concrete paving machine, as a result of which this dowel apparatus can be kept small and light-weight in relation to the dimensions of the entire concrete paving machine. The dowel apparatus which, as will become clear from the further description, is rather complex and also takes up relatively much space in the height, then can, due to its relatively small width, easily be transported to the site where it has to be used or can easily be mounted permanently at the concrete paving machine.
According to a particular embodiment of the invention, the dowel apparatus is mounted to the paving machine at such a height that it is located at a distance above the upper surface of the levelled concrete, resulting in that there is no contact between the concrete and the lower portion of the dowel apparatus. In this way, amongst others, the advantage is attained that the frame of the dowel apparatus cannot cause irregularities in the surface of the concrete, contrary to the devices disclosed in EP 0.051.885, EP 0.196.698 and DE 3.811.186, in which at the location of the dowel apparatus always a slide is provided which is in contact with the concrete.
A feature that the dowel apparatus is mounted freely above the concrete is particularly advantageous in combination with the dowel apparatus which is movable according to the working width, but, according to the present invention, can also be applied in concrete paving machines having a dowel apparatus which is not movable according to the working width, for example, a dowel apparatus extending over the complete width of the machine.
According to another particular feature of the invention, the machine is provided with means for automatically controlling and adjusting the distance between the lower portion of the dowel apparatus and the surface of the levelled concrete. These means may consist of detection means to control the height of the dowel apparatus in respect to the upper surface of the concrete and of driving means to bring at least a lower portion of the dowel apparatus at the required height. Preferably, the adjustment is done automatically, such that the distance remains constant.